From the state of the art, such machine tool gear mechanisms are known. They typically comprise a two-stage planetary gear system and a corresponding shifting device, such as that described in WO 00/63569, so that rotational speed differentials in the gear ratio are produced between the input or the motor shaft and the output. The torque is transmitted from the output shaft of the gear mechanism directly to the spindle, wherein the spindle is preferably disposed co-axially to the output shaft. In such gear mechanisms, the output shaft is directly connected to the spindle; the rotationally fixed connection between the spindle and output shaft may be achieved with positive or non-positive fit. Hereby, it is necessary to provide a delivery device for coolants, emulsions, oils or air between the gear mechanism output and the spindle.
From DE 42 20 310 C2 a working spindle of a machine tool is known, where the spindle and the bearings of the spindle in the machine tool head are cooled by a forced air stream, the volume of the air current is proportional to the rotational speed of the spindle and where a turbine or nozzle wheel is provided for producing the air current. The wheel is effectively connected to the spindle.
For machine tool gear mechanisms known from the state of the art it has been proposed (older German patent application by the Applicant DE 102 004 003 685.3) to integrate a rotary passage in the gear mechanism output shaft, the passage serving as a delivery device for coolants, emulsions, oils or air between the gear mechanism output and the spindle. A dynamic sealing point is provided for absorbing the volumes and the resulting pressure. The rotary passage is integrated in the output shaft and comprises two sealing disks, which serve as the sealing point and as a device for absorbing rotational speed differentials. The sealing disks may comprise different materials and/or have different geometries and fastening elements as a function of the medium, the developing pressure and the volume flows.
In this design, the influence of the out-of-balance value, which is caused by the imprecise output shaft bearings compared to the spindle bearings, is negatively influenced due to the integration of the rotary passage in the output shaft.
It is, therefore, the object of the invention to provide a machine tool gear mechanism, particularly a spindle gear mechanism, wherein torque is transmitted from the output shaft of the gear mechanism directly to the spindle, the mechanism comprising a rotary passage for the delivery of coolants, emulsions, oils or air between the gear mechanism output and the spindle, wherein the influence of the out-of-balance value is reduced compared to the state of the art. Furthermore, simple assembly is to be guaranteed.